1. Field of the Invention
The present invention relates generally to improvements in measuring devices that utilize background lighting and methods of constructing such measuring devices. More specifically, the invention relates to a device such as a sheet dimension gauge and a method of constructing a sheet dimension gauge which does not require recalibration.
2. Description of Related Art
Many measuring devices that utilize background lighting rely on the accuracy of the measurement lines which are generally overlaid onto a transparent surface one flaw in such measuring devices is that the heat generated by the lights may cause the device to be inaccurate. The heat generated from the lights cause the transparent surface to expand, such expansion often occurring in an uneven manner due to hot spots on the transparent surface. Many of these devices have frames that are constructed of materials which expand and contract due to changes in humidity, which further adds to their inaccuracy. Even frequent recalibration will not ensure that the device is accurate.
One such measuring device is a paper dimension gauge which is used to quickly and easily check whether a sheet of paper is manufactured to the proper specifications. Some manufacturers claim to produce paper dimension gauges which can measure to within 0.002 inches. However, many paper dimension gauges are constructed of several different types of materials which are supposed to act in unison to measure a sheet of paper. Unfortunately, many paper dimension gauges are constructed of materials whose dimensions are susceptible to changes in humidity and temperature. Therefore, any slight fluctuation in temperature and humidity has an affect on the paper dimension gauge's calibration and can potentially destroy the gauge's accuracy.
The present invention is directed at solving the perceived need for a measuring device, such as sheet dimension gauges used to measure paper, film, or other materials, and a method of constructing a measuring device such that the device does not require recalibration. The measuring device should be constructed of materials whose dimensions are not susceptible to changes in humidity. The measuring device should also be capable of maintaining a uniform and constant predetermined temperature during operation and the device should be constructed and originally calibrated at that temperature to ensure proper calibration. The measurement device should have a one piece measurement guide rigidly mounted on the device in relation to the measurement lines in order to maintain the correct calibration. The measuring device should also include a protective cover to prevent the measurement lines from becoming damaged.
The following publications describe devices which utilize background lighting. U.S. Pat. No. 1,267,055, issued on May 21, 1918, to Robert M. Cathcart; U.S. Pat. No. 2,034,529, issued on Mar. 17, 1936, to Oswald A. Olsen; U.S. Pat. No. 2,378,249, issued on Jun. 12, 1945, to Roger A. Ruth; U.S. Pat. NO. 2,380,267, issued on Jul. 10, 1945, to Roger A. Ruth; U.S. Pat. No. 2,413,198, Dec. 24, 1946, to James A. Stewart; U.S. Pat. No. 2,444,723, issued on Jul. 6, 1948, to Everette F. Bowen; U.S. Pat. NO. 2,643,326, issued on Jun. 23, 1953, to Joseph F. Knapp; U.S. Pat. No. 3,355,810, issued on Dec. 5, 1967, to Earl W. Franklin; U.S. Pat. No. 3,410,994, issued on Nov. 12, 1968, to Louis A. Facto; U.S. Pat. NO. 3,532,018, issued on Oct. 6, 1970, to Francis S. Szabo; U.S. Pat. No. 3,704 067, issued on Nov. 28, 1972, to William R. Womack; U.S. Pat. No. 4,507,714, issued on Mar. 26, 1985, to William T. Aschinger et al.; U.S. Pat. No. 4,769,747, issued on Sep. 6, 1988, to Louis C. Parrillo; United Kingdom Patent Application Number 937,351, published on Sep. 18, 1963; United Kingdom Patent Application Number 1,048,521, published on Nov. 16, 1966.
The above listed publications fail to describe the benefits of a temperature control system within the device for maintaining the accuracy of the device and the benefits of manufacturing the measuring surface at the device's operating temperature. The above listed publications also fail to describe the benefits of using material whose dimensions are not susceptible to changes in humidity. They also fail to describe the benefits of using a cover to protect the measurement surface of the device.
For general information on paper dimension gauges, a product brochure by QUICK SKAN, 826 South Fairview, Park Ridge, Ill. 60068 shows several models of paper dimension gauges. Additionally, the inventor has knowledge of the existence of a paper dimension gauge with an aluminum frame manufactured in Germany.
None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus a measurement device and method of constructing such device solving the aforementioned problems is desired.